Preferably, exterior aircraft surfaces should be aerodynamically smooth and aesthetically pleasing. Current (conventional) assembly processes typically utilize two-sided fasteners such as solid rivets, lock bolts with collars, and threaded pins with nuts. The manufactured heads of these installed fasteners are often positioned on the airflow surfaces of the aircraft. Their construction means that the exposed surface(s) can be easily painted with acceptable results because of the absence of head surface discontinuities.
Newer generation aircraft are to be assembled robotically, and it is not practical to install conventional two-sided fasteners such as solid rivets, lock bolts and threaded pins with this type of equipment. The primary issue with robotic assembly is the equipment cost and programming coordination. The requisite equipment is essentially doubled due to requiring equipment on each side so as to have access to each end of the fastener. Further, the timing and synchronization of the equipment on one side has to be coordinated with the timing and synchronization of the equipment on the opposite side. As a result, a need exists for blind (one-sided) fasteners that are easily installed with a robot, and optionally shaved, but also leave a flaw free head surface that may be painted with a good quality finish.
There are many types of blind fasteners presently available for assembly of aircraft structures and components, but these fasteners have drawbacks that make their use in many of the painted aerodynamic applications that are emerging less than optimal. Mechanically-locked pull-type blind rivets generally fail to provide sufficient joint strength. Mechanically-locked pull-type blind bolts, as disclosed in U.S. Pat. No. 4,127,345, issued Nov. 28, 1978 to Angelosanto et al., and rivets, as disclosed in U.S. Pat. No. 5,378,098, issued Jan. 3, 1995 to Andrews et al., typically incorporate a locking ring in the manufactured head that must not be shaved smooth, lest the structural integrity of the fastener would be adversely affected. Threaded blind bolts, as disclosed in U.S. Pat. No. 4,457,652, issued Jul. 3, 1984 to Pratt, may have sufficient strength but leave a small discontinuity on the head surface after shaving, resulting from gaps between male and females threads. The concern over having a discontinuity of this type is that the negative aesthetics are exaggerated by the application of paint. This discontinuity arises from small, but necessary, clearances between the female and male threads of the fastener.